This invention relates to hydraulic pumping systems and, more particularly, to such systems which are driven by flowing water at low head to develop a higher water pressure than that which is initially available.
Many systems have been developed for intensifying available fluid pressure to create an elevated fluid pressure without resort to the consumption of energy in a driving means to do the work of pressure intensification. In such systems of interest here, the fluid is liquid, normally water from a stream or other source which is available at relatively limited pressure head and which is utilized to provide a portion of the available water at an elevated pressure which may be several times the differential head pressure.
Systems of the type described may be broadly classified in two categories: those such as a hydraulic impulse ram system which makes use of the kinetic energy of water flowing in a pipe to raise part of the water to a higher level, and those which utilize intercoupled pistons/cylinders having different cross sectional areas which achieve pressure multiplication in proportion to the ratio of the respective piston areas. The systems of the present invention are of the latter category.
Systems of the latter category are exemplified in U.S. Pat. Nos. 217,626 to Lyman, 2,080,695 to Cargile, 2,579,670 to Hjarpe, 2,864,313 to Dawson and 2,896,542 to Forghieri. All of these disclose a pair of pistons of differing diameters mounted at opposite ends of a single connecting rod and operable in corresponding dual cylinder configurations. Control valve means are associated with these dual piston arrangements to supply and release water to and from the respective cylinders in appropriate synchronism so that the larger piston, operating at low relative pressure, drives the smaller piston, operating at increased relative pressure, to provide water at a pressure head substantially above that of the driving liquid which is available. The Hjarpe patent discloses two pairs of differential pistons operating in opposite phase to each other so that a more even pressure at the output of the system may be achieved.
All of the disclosed systems, except that of Dawson, utilize control valving arrangements which are mounted internally of their main piston housing. By means of these internal control valves, water from the associated low pressure source is alternately directed into the larger cylinder to drive the piston therein through the extent of its travel and then released from the larger cylinder while the dual pistons are returned to the bottom of their stroke by pressure from the source being applied to the smaller piston as its cylinder is filled with water for the next pressure amplifying stroke. During the release mode, water from the larger cylinder is typically returned to the stream from which it came by gravity flow.
The Dawson patent discloses a separate control valve in the form of a spool valve mounted in a separate chamber which is interconnected with the pressure intensifying chamber through a plurality of tubes. Water from the low pressure source is first directed to the spool valve chambers prior to being directed to the piston housing to drive the intensifying pump. Dawson's pump has a double acting main piston with water being applied directly to one side or the other of the main piston in order to control its reciprocating movement. During the return stroke, water from the underside of the piston is returned through the spool valve before being exhausted from the system.
An apparent limitation of those prior art systems which are known is the inability to increase the quantity of liquid which is provided at the intensified pressure without modification of the system. Pressure multiplication is a function of the ratio of the piston areas, and the quantity of water provided depends on the flow rate of the system as constructed and the rate at which the pistons can be cycled, which in turn is a function of available differential pressure. Where the available pressure head is minimal, the rate of flow is those systems which are referenced hereinabove is also limited.